142
The Biology of Sea Turtles, Vol. II
5.4.3 C OURTSHIP AND S CRAMBLE P OLYGAMY
Male sea turtles are generally promiscuous seasonal breeders, and exhibit scramble
mate-finding tactics (Ehrhart, 1982; Limpus, 1993; FitzSimmons, 1997; Jessop et al.,
1999a). Similar to females, they are migratory and show strong site fidelity to both
courtship and foraging areas (Limpus, 1993; FitzSimmons, 1997). Courtship appears
to be confined to a distinct period just prior to the start of the nesting season (Ehrhart,
1982; Owens and Morris, 1985; Limpus, 1993), and male C. mydas appear to spend
around 30 days searching for a mate (Wood and Wood, 1980; Limpus, 1993). In the
most comprehensively studied population to date (C. mydas in the southern GBR,
Australia) males may travel considerable distances searching for potential mates,
and recapture distances are further afield in breeding as opposed to nonbreeding
males (80% of recaptures were within 3650 and 1900 m of the initial capture site,
respectively) (FitzSimmons, 1997). Competition between males has been recorded
in many courtship areas (Booth and Peters, 1972; Balazs, 1980; Limpus, 1993;
FitzSimmons, 1997; Miller, 1997). In some species and areas, aggressive male-tomale and male-to-female courtship activities have also been noted, one example
being the black turtle (Chelonia agassizi) of the eastern Pacific (Alvarado and
Figueroa, 1989). In general, male sea turtles show limited male-to-male aggression,
and the number of attendant males with each mounted pair and the range of courtship
damage on males appear to fluctuate annually.
5.4.4 REGULATION OF COURTSHIP
Both male and female sea turtles are capital breeders, i.e., they store energy that can
be later mobilized for reproduction (Stearns, 1989). Recently Jessop et al. (1999a)
and Jessop (2000) proposed that the reproductive fitness of a particular male was
likely to be status-dependent. Briefly, high-status males (those with higher somatic
energy stores and elevated levels of testosterone) were most likely to have higher
intensity mate-searching behavior and therefore be exposed to more females in a
given amount of time. The associated tradeoff is almost certainly the increased
energetic cost involved in such high-intensity scramble mating. Males exhibiting
high-intensity courtship may reach their refractory period earlier and thus have a
lesser period in which to find females. Alternatively, some males may adopt less
energetic courtship strategies, and although these males may not search as large an
area, they will be able to actively participate in mate searching and mate acquisition
for longer. Courtship aggregations may show significant intra- and interannual variation in the density and ratio of breeding males and receptive females.
The courtship tactics used by males (high- or low-intensity scramble) may vary
annually in their effectiveness at locating as many females as possible while maintaining metabolic homeostasis. In years of low-density courtship, high-intensity
scramble behavior may result in higher reproductive success, whereas in high-density
years, a lower (medium) scramble tactic may be the most appropriate (Jessop, 2000).
From a metabolic viewpoint it also appears that the cessation of the courtship is
marked by significant changes such as decreased body condition, identifiable as
lowered plasma triglyceride levels and increased plasma protein levels (Hamann and
Jessop, unpublished data); however, these relationships need further validation.
1123 book.book Page 142 Thursday, November 14, 2002 11:50 AM
The Biology of Sea Turtles, Vol. II
5.4.3 C OURTSHIP AND S CRAMBLE P OLYGAMY
Male sea turtles are generally promiscuous seasonal breeders, and exhibit scramble
mate-finding tactics (Ehrhart, 1982; Limpus, 1993; FitzSimmons, 1997; Jessop et al.,
1999a). Similar to females, they are migratory and show strong site fidelity to both
courtship and foraging areas (Limpus, 1993; FitzSimmons, 1997). Courtship appears
to be confined to a distinct period just prior to the start of the nesting season (Ehrhart,
1982; Owens and Morris, 1985; Limpus, 1993), and male C. mydas appear to spend
around 30 days searching for a mate (Wood and Wood, 1980; Limpus, 1993). In the
most comprehensively studied population to date (C. mydas in the southern GBR,
Australia) males may travel considerable distances searching for potential mates,
and recapture distances are further afield in breeding as opposed to nonbreeding
males (80% of recaptures were within 3650 and 1900 m of the initial capture site,
respectively) (FitzSimmons, 1997). Competition between males has been recorded
in many courtship areas (Booth and Peters, 1972; Balazs, 1980; Limpus, 1993;
FitzSimmons, 1997; Miller, 1997). In some species and areas, aggressive male-tomale and male-to-female courtship activities have also been noted, one example
being the black turtle (Chelonia agassizi) of the eastern Pacific (Alvarado and
Figueroa, 1989). In general, male sea turtles show limited male-to-male aggression,
and the number of attendant males with each mounted pair and the range of courtship
damage on males appear to fluctuate annually.
5.4.4 REGULATION OF COURTSHIP
Both male and female sea turtles are capital breeders, i.e., they store energy that can
be later mobilized for reproduction (Stearns, 1989). Recently Jessop et al. (1999a)
and Jessop (2000) proposed that the reproductive fitness of a particular male was
likely to be status-dependent. Briefly, high-status males (those with higher somatic
energy stores and elevated levels of testosterone) were most likely to have higher
intensity mate-searching behavior and therefore be exposed to more females in a
given amount of time. The associated tradeoff is almost certainly the increased
energetic cost involved in such high-intensity scramble mating. Males exhibiting
high-intensity courtship may reach their refractory period earlier and thus have a
lesser period in which to find females. Alternatively, some males may adopt less
energetic courtship strategies, and although these males may not search as large an
area, they will be able to actively participate in mate searching and mate acquisition
for longer. Courtship aggregations may show significant intra- and interannual variation in the density and ratio of breeding males and receptive females.
The courtship tactics used by males (high- or low-intensity scramble) may vary
annually in their effectiveness at locating as many females as possible while maintaining metabolic homeostasis. In years of low-density courtship, high-intensity
scramble behavior may result in higher reproductive success, whereas in high-density
years, a lower (medium) scramble tactic may be the most appropriate (Jessop, 2000).
From a metabolic viewpoint it also appears that the cessation of the courtship is
marked by significant changes such as decreased body condition, identifiable as
lowered plasma triglyceride levels and increased plasma protein levels (Hamann and
Jessop, unpublished data); however, these relationships need further validation.
1123 book.book Page 142 Thursday, November 14, 2002 11:50 AM